Non-malleable cryptography

Abstract

The notion of non-malleable cryptography, an extension of semantically secure cryptography, is defined. Informally, the additional requirement is that given the ciphertext it is impossible to generate a different ciphertext so that the respective plaintexts are related. The same concept makes sense in the contexts of string commitment and zero-knowledge proofs of possession of knowledge. Non-malleable schemes for each of these three problems are presented. The schemes do not assume a trusted center; a user need not know anything about the number or identity of other system users. Keywords: cryptography, cryptanalysis, randomized algorithms, nonmalleability AMS subject classifications: 68M10, 68Q20, 68Q22, 68R05, 68R10 A preliminary version of this work appeared in STOC '91 Hebrew University Jerusalem, Israel y IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, CA 95120. E-mail: [email protected]. z Incumbent of the Morris and Rose Goldman Career Devel...